The present invention relates generally to integrated circuit devices, and more particularly, to a method for making a semiconductor structure having an alpha particle resistant film and to such semiconductor structures.
In the manufacture of integrated circuits, semiconductor wafers containing many separate integrated circuits are fabricated and then cut into individual integrated circuits, often individually referred to as die. It is well known that the die may be adversely affected by alpha particles, such as those alpha particles which are emitted from metals, ceramics, as well as some plastic materials. When such alpha particles impinge on a semiconductor memory cell, a change may result in the state of a bit within the memory cell, resulting in a phenomenon known in the industry as a "soft bit error". Although this type of error may be corrected using known error correction and detection schemes, multiple "soft bit errors" may create conditions in which such schemes are unable to provide a desired correction. Thus, it is desirable to protect integrated circuit die which are subject to degradation by alpha particles.
The need to provide alpha particle protection has become more critical as the density of integrated circuits increases. Although there are available methods for providing some degree of alpha particle protection, none of these methods is totally satisfactory inasmuch as such methods present certain disadvantages and/or require cumbersome processing techniques. For example, one technique includes the application of liquid polyimide on the individual die after the die has been attached to a substrate and wire bonded. This technique requires substantial labor while providing a high die rejection rate. Further, this liquid system does not reliably provide a sufficient thickness of the protective coating near the edges of the area to be protected. Other techniques attempt to screen print liquid polyimide in a pattern on the semiconductor wafer itself. However, such techniques have been hampered by the inability to print polyimide in sufficient thicknesses. Generally, in addition to their high failure rate, steps of dispensing and applying liquid or paste are difficult to automate.
Accordingly, it is a general object of this invention to provide an improved method for providing a semiconductor structure with alpha particle resistance and to provide such semiconductor structures.
Another object of the present invention is to provide such a method and structure which reduces the problems involved in the use of paste or liquid alpha particle resistant materials.
Another object of this invention is to provide such a method which can be automated.